Hydraulic lifting jacks

ABSTRACT

A hydraulically operated telescopic lifting jack comprises a piston carrying a ram-head which houses a non-return valve, a pressure relief valve and a fluid-release valve. The fluid release valve includes a slide member carrying a valve member and mounted in a guide. A portion of the slide member is of reduced diameter in relation to the guide and defines therewith a chamber which communicates with a fluid feed connection.

llited States Wenzel et a1,

a tent 1 HYDRAULIC LIFTING JACKS lnventors: Jiirg Wenzel,

Freudenberg/Main-1(irschfurt; Hans Rieschel, Miltenberg/Main, both ofGermany [73] Assignee: Josef Haamann, Freudenberger Winden-UndHebezeugfabriir, MainJCirschfurt, Germany [22] Filed: May 7, 1971 21App]. N0.: 141,146

60/97 E, 97 L, 52 US, 52 HC, 52 HB, 52 HA [56] References Cited UNITEDSTATES PATENTS 2,618,929 11/1952 Bidin 60/52 HA 3,134,232 5/1964 Barosko2,657,533 11/1953 Schanzlin et a1. 60/52 HC Primary Examiner-Edgar W.Geoghegan Azt0rneyMason, Mason & Albright ABSTRACT A hydraulicallyoperated telescopic lifting jack comprises a piston carrying a ram-headwhich houses a nonreturn valve, a pressure relief valve and afluid-release valve. The fluid release valve includes a slide membercarrying a valve member and mounted in a guide. A portion of the slidemember is of reduced diameter in relation to the guide and definestherewith a chamber which communicates with a fluid feed connection.

3 Claims, 2 Drawing Figures 14 I I 87 81. '85 82 31 57 l 13 I P 1. i

HYDRAULIC LIFTING JACKS BACKGROUNIh OF THE INVENTION and distributionequipment and is connected by two pressure lines to each of the fourjacks with the aid of hydraulic quick-release couplings. While such anarrangement allows one-man operation, this applies only to the actionsof lifting, holding and lowering, and not to the diverse operations ofattaching the load to the jacks themselves and releasing it from them.These operations have to be carried out individually at each loadattachment point and presuppose that each jack can be extended andretracted independently of the others and hence also independently of acentral distribution system.

Moreover, loading operations often require that a jacked-up containershall be left standing for a time. There are consequently several setsof four jacks in use. On the other hand, it is uneconomic to keepavailable for every jack an installation of its own, with a compressorand distribution arrangements, which ought instead to be transferableaccording to need. This requirement makes further demands on thedistribution system, since the jacks have to retain their pressureindependently of the compressor while under load, yet must be bothraised and lowered either by remote or by manual control.

An object of the invention is to provide a hydraulic telescopic jackhaving a ram-head which can be supplied with pressure fluid, and hencemoved, by the use of only two pressure lines from a centralinstallation, its movements can be both purely hydraulicallyremotecontrolled and manually controlled and it can maintain theposition in which it is set for as long as desired, even while underload and disconnected from the central installation.

SUMMARY OF THE INVENTION According to the invention, there is providedin a hydraulically-operated telescopic lifting jack, a cylinder, apiston slidable within the cylinder, a ram-head carried by the piston, afirst connection for hydraulic fluid, means defining a path forhydraulic fluid through the ram-head between said first connection andsaid cylinder, valve means mounted on said ram-head and controlling theflow of hydraulic fluid along said path, said valve means including anon-return valve, an overpressure valve, and a lowering valve, saidlowering valve comprising means defining a guide in said ramhead, aslide member mounted in said guide, a portion of said slide member beingof reduced diameter in relation to said guide to define piston means,andsaid portion defining with said guide a chamber,-a second connection forhydraulic fluid, and means defining a passage extending between saidchamber and said second connection.

Further according to the invention, there is provided in a hydraulicallyoperated telescopic lifting jack, a cylinder, a piston slidable withinthe cylinder, first and second feed connections for hydraulic fluid,means defining a fluid path between said first feed connection and saidcylinder, a non-return valve in said path permitting flow of fluid intosaid cylinder, a pressure-relief valve controlling the maximum pressureof fluid flowing along said path, a fluid-release valve for releasingfluid from said cylinder and comprising cylinder means, piston meansslidable in said cylinder means, and a valve member rigid with saidpiston means, and means defining a fluid path between said secondconnection and said cylinder means, so that fluid can be fed into saidcylinder means to move said piston means in a sense to open said valvemember.

Preferably, to extend the jack the ram-head is secured by means of pegsor other connecting members in a recess in the part that is to belifted, pressure fluid fed from a pump is forced into the cylinder froma central distribution system through a Lift" control valve. Flowback ofthe fluid thus pumped in is prevented by the non-return valve as soon asthe pressure in the feed line is removed, so that the ram-head ishydraulically locked at the level to which it has been raised and staysthere.

Preferably, in order to be able to raise the jack manually at will, asis necessary in adjusting and securing it at the load-lifting point,there is provided in or on the ram-head, a pre-control valve that can beclosed at will and which is generally open. For adjustment purposes,however, this pre-control valve is closed, the feed line then beingbrought under pressure from distribution system through the Lift controlvalve. By careful' opening of the pre-control valve, the jack can beextended slowly and very precisely, as required. This procedure can becarried out individually at each of the load lifting points with each ofthe jacks positioned thereat. Once all the jacks have been adjusted, thecontrol valve is returned to its closed position and the precontrolvalves are opened once more; the installation is then in working order,ready to lift the load and to hold, transfer or set it down as required.

In one preferred embodiment of the invention, the pre-control valve is athree-way valve, which connects either the feed-line connection or thedistributionsystem connection to the cylinder or to a passage incommunication therewith. In this manner, it is possible for the jack tobe manually lowered, by opening the lowering valve, even when the feedline is under pressure. To begin with, the pressure-carrying feed lineis cut off by operation of the pre-control valve; the ram will notcontinue to move out. Then, if the lowering valve also be operated, thejack can be lowered even while the feed line is still full.

BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the invention will nowbe described, by way of example, with reference to the accompanyingdiagrammatic drawings, in which:

FIG. I is a longitudinal section of a jack in accordance with theinvention; and

FIG. 2 is a fragmentary section through a modified form of the jackshown-in FIG. 1, and shows a block diagram of a central distributionsystem.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in the drawings, thejack comprises a lifting ram having a cylinder 1 which is inserted in asupporting foot (not shown) and a hollow piston 2 which is movable alonglongitudinal guides in the cylinder 1. Mounted in the head 3 of the ramare the necessary valves, namely a non-return valve 4 in the form ofspring-loaded ball valve, an overpressure valve 5 in the form of aspring-loaded conical valve, a lowering valve 6, and a pre-control valve7. The non-return and overpressure valves, which lie co-axially onebehind the other and are joined together by a passage 81, are housedwithin a slide member 8 of the lowering valve 6, with the non-returnvalve 4 inside the head 88 of the member 8 and the overpressure valve 5nearer to the tail portion 89 thereof. The passage 81 is incommunication, through a radial opening 82, with a chamber 9, whichaccommodates a restoring spring of the lowering valve 6 and is incommunication, through a passage 31, in the ram-head 3, with theinterior of the hollow piston and the cylinder.

The tail end portion 89 of the slide member 8, that is to say the endportion of the slide member 8 remote from its head 88, is reduced indiameter and made leakproof by packing rings 83 and 84. The tail endportion 89 of the slide member 8 projects out of the ram-head and hasits end face bearing against a cam 11, which is mounted in a bifurcation32 of the ram-head for pivotal movement about a pin 12, under the actionof a hand lever 13.

By means of the packing rings 83 and 84 and a seat 85 of the loweringvalve 6 constituted by the head 88, the slide member 8 forms threechambers in the ramhead 3, namely: a central chamber 9 a chamber 14surrounding the reduced-diameter tail end portion 89, in which theshoulder of the reduced-diameter portion forms a ring-shaped plungerface 86, and which communicates with the atmosphere through a passage 33in the ram-head 3; and a chamber 15 which contains the head 88 of theslide member 8 and has an opening 34, leading to-the exterior.

Mounted on the ram-head 3, over the opening 34 in the chamber 15, is acasing 77 of the pre-control valve 7, the spindle 71 of which can bemoved axially in a screwthread 73 by means of a handwheel 72, so that aconical valve-member can close or open a passage 74 which providescommunication between the opening 34 and a connection 75 for a pressurefeed line P. The chamber 14 communicates, via a passage 33 with aconnection 76 for a pipe R.

A central distribution system ST incorporates two pumps PU connected inparallel but independent of each other, which feed four hydraulic onlyone shown jacks. The pressure connections of both pumps are branched viadistribution valves STV to serve two jacks each. Of the four jacks beingapplied at any moment to a load, the two opposite each other at one endof the load are served by one pump, the same applying to the pair ofjacks at the other end of the load. Differences between the lift andlower movements of two jacks on the same side of the load but atdifferent ends, on the other hand, require to be levelled out throughthe distribution system.

As will be immediately apparent, if a leak should occur at any point inthe hydraulic system, the nonreturn valve 4 can still be relied on toshut off the fluid contained in the cylinder and piston space, so thatthe jack will still hold its load. It is therefore possible for thejack, when under full load, to be separated from the hydraulic system bytwo quick-release couplings, SK, in the two pipes P and R, so as toenable the same distribution system, ST for instance, to be used inconjunction with a different set of four jacks for lifting a secondcontainer or other load.

REMOTE CONTROL When the distribution valve STV in the distributionsystem ST is moved from its neutral central position to a Lift position,the pump PU driven by a motor or internal-combustion engine M forexample, drives fluid under pressure from a tank T through the feed pipeP and the normally open pre-control valve 7, into the chamber 15 in theram-head 3. From the chamber 15, the lowering valve 6 being closed, thefluid overcomes the opposition of the non-return valve 4 and flows alongthe passage 81 and through the radial opening 82 into the centralchamber 9, whence it passes by way of the passage 31 into thecylinder 1. The hollow piston 2 rises under the pressure exerted on itsend face for as long as the valve STV remains in its Lift position, oruntil a piston ring 21 abuts an inner shoulder 101 of a cylinder collar102. When the pressure within the cylinder is likely to exceed thepermitted maximum pressure the overpressure valve 5 at the rear of thepassage 81 in the tail end portion 89 of the slide member 8 opens andthe fluid fed in flows through a radial opening 87 behind a conicalvalve member 57 of the valve 5 into the rear chamber 14 and from therethrough the passage 33 and the pipe R, attached to the connection 76,returns to the tank T.

To lower the ram, the distribution valve STV is moved to a Lowerposition, the fluid fed by the pump PU then being driven, through thepipe R and the passage 33 into the chamber 14, where the pressure of thefluid acts on the ring-shaped plunger face 86, so that the slide member8 is moved to the left (as viewed in the Figures). This movement opensthe lowering valve 6 and the fluid in the cylinder and piston space isforced by the loaded piston 2 through the chamber 15 and the passage 74back into the pipe P through which it passes to the tank T.

MANUAL CONTROL To raise the jack manually, the pre-control valve 7 isfirst closed by means of the handwheel 72. Next, the distribution valveSTV in the distribution system ST is moved to its Lift" position, sothat fluid is delivered under pressure, by way of the pipe P, at the nowclosed pre-control valve 7. By careful unscrewing of the valve spindle71 to a certain extent, the passage 74 is opened to a certain extent sothat pressure fluid is fed as described previously into the cylinderspace and the piston 2 rises. This upward movement can be stopped byclosing the valve 7, whatever the position of the piston, and the pistonis then hydraulically locked in that position.

For central remote control (a number of jacks being jointly andsimultaneously controlled), the distribution valve STV is once moremoved to its central position, whereupon the pre-control valve 7 isopened to its full extent.

To lower the piston manually, the lever 13 is pivoted causing the cam 11to thrust the slide member 8 of the lowering valve 6 to the left wherebyto open the valve 6, so that the fluid in the cylinder and piston spaceis forced by the load on the piston into the chamber and from there intothe pipe P. This, of course, presupposes that the pipe P is not underpressure, for which reason the distribution valve ST V must be set toLower.

This additional change-over in the distribution system ST is superfluouswhen the pre-control valve is of the three-way type, as is shown in theembodiment FIG. 2, in which the construction of the ram-head 3 and thearrangement of the valves and of passages in the ramhead 3 are the sameas in FIG. 1, like parts in the two embodiments being designated by thesame reference numerals. In the embodiment shown in FIG. 2, theprecontrol valve 7 connects the opening 34 in the chamber 15 in theram-head casing 3 either to the pipe P or to the pipe R, the path to theother pipe being closed in each case.

If, when the ram is being lowered by operation of the lever 13, thefluid cannot escape via the pipe P from the cylinder and piston spacebecause the pipe P is blocked within the distribution system ST, thepath to this pipe can be blocked through the pre-control valve 7 and apath opened to the pipe R instead, which is open in the basic positionof the distribution valve STV, so that the excess fluid from thecylinder can flow through the pipe R into the tank T.

The invention is not limited to the two practical examples illustratedand described. In particular, the construction and arrangement of thevarious valves may be different although the coaxial arrangement of thevalves is preferable, because it results in a particularly smallram-head constructionand is specially suitable for the use of a normalhydraulic pit prop, which merely requires the addition of thepre-control valve, while the tail end portion of the slide member of thelowering valve must be reduced in diameter so as to form a ringshapedplunger face. It will also be appreciated that the pre-control valveneed not necessarily be mounted in or on the ram-head, provided it behydraulically connected to the feed aperture thereof.

What is claimed is: 1. In a hydraulically-operated telescopic liftingjack, a cylinder, a piston slidable within the cylinder, a ram-headcarried by the piston, a first connection for hydraulic fluid, meansdefining a path for hydraulic fluid through the ram-head between saidfirst connection and said cylinder, valve means mounted on said ram-headand controlling the flow of hydraulic fluid along said path, sai valvemeans including a non-return valve, an overpressure valve, and alowering valve, said lowering valve comprising: means defining a guidein said ram-head, and a slide member mounted in said guide, a portion ofsaid slide member being of reduced diameter in relation to said guide todefine piston means, and said portion defining with said guide achamber, a second connection for hydraulic fluid, and means defining apassage extending between said chamber and said second connection. 2. Ajack as claimed in claim ll, comprising: a pre-control valve, which canbe opened at will, carried by said ram-head beyond said firstconnection. 3. A jack as claimed in claim 2 comprising means defining afurther chamber in said ram-head, said further chamber housing saidnon-return valve and said lowering valve, and wherein said precontrolvalve is a three-way valve and selectively connects either one of saidfirst and second connections to said further chamber.

1. In a hydraulically-operated telescopic lifting jack, a cylinder, apiston slidable within the cylinder, a ram-head carried by the piston, afirst connection for hydraulic fluid, means defining a path forhydraulic fluid through the ram-head between said first connection andsaid cylinder, valve means mounted on said ram-head and controlling theflow of hydraulic fluid along said path, said valve means including anon-return valve, an overpressure valve, and a lowering valve, saidlowering valve comprising: means defining a guide in said ram-head, anda slide member mounted in said guide, a portion of said slide memberbeing of reduced diameter in relation to said guide to define pistonmeans, and said portion defining with said guide a chamber, a secondconnection for hydraulic fluid, and means defining a passage extendingbetween said chamber and said second connection.
 2. A jack as claimed inclaim 1, comprising: a pre-control valve, which can be opened at will,carried by said ram-head beyond said first connection.
 3. A jack asclaimed in claim 2 comprising means defining a further chamber in saidram-head, said further chamber housing said non-return valve and saidlowering valve, and wherein said pre-control valve is a three-way valveand selectively connects either one of said first and second connectionsto said further chamber.